Army Corps: Plants in riverbed could cause severe flooding

By: PAUL SISSON - Staff Writer | Saturday, November 19, 2005 11:00 PM PST ∞

OCEANSIDE ---- The U.S. Army Corps of engineers says the overgrown San Luis Rey River channel in Oceanside is a disaster waiting to happen.

A letter sent from the Corps' Los Angeles office to headquarters in Washington, D.C., warns that out-of-control vegetation in the San Luis Rey riverbed is so bad that a 100-year flood could cause the river's protective levees to fail, resulting in "flood damages throughout the area which are estimated to be at least $185 million."

According to the Federal Emergency Management Agency, a 100-year flood is defined as a flood that has a 1 percent chance of occurring in any given year.

Written on Sept. 27 by Col. Alex Dornstauder, commanding engineer of the Army Corps' Los Angeles office, the letter asks the Corps' headquarters for "emergency action" to clear a 200-foot-wide, 7-mile-long swath of vegetation from the San Luis Rey River channel in order to temporarily restore the river's flood-carrying capacity.

The letter also asks for a $10 million in federal money to pay for clearing efforts.

City preparing
City officials in Oceanside aren't waiting for the federal government to step in with assistance.

City Manager Steve Jepsen and Public Works Director Peter Weiss asked the City Council in a memorandum last week to declare a "threatened local disaster for the San Luis Rey River" at its next regular meeting on Dec. 7. The declaration would allow the city to begin mobilizing its resources to clear the channel now, rather than waiting until it gets an official nod from the Corps.

The memorandum envisions a scenario this winter in which heavy rains could dislodge vegetation in the river channel and send it downstream.

"As the vegetation washes out, it will accumulate on the bridges crossing the river," the city memo states. "As the vegetation accumulates against the bridges, the damming effect has the potential to overtop the levee and to damage or destroy the bridges."

City officials said last week that in all likelihood the Corps won't be able to move quickly enough in authorizing clearing before this year's storm season begins. Weiss said the city has the authority through its city codes to declare the threat of a disaster and solicit bids to clear the minimum amount of vegetation from the river channel to ensure that it can convey a deluge to the ocean without flooding the San Luis Rey River Valley along the way.

Weiss said that the city would not necessarily act on its own without an OK from the Army Corps of Engineers, but a resolution from the council to solicit bids would allow the city to be ready if and when that approval comes.

"All we would need is someone to push the 'go' button," Weiss said.

Like any other storm drain, the levee is armored with concrete and heavy rocks, creating a hard surface that can contain swift water. However, city officials note that the levee's backside isn't shored up by concrete and heavy rocks, and that that lack of protection presents a potential weak spot for flood water.

"As water overtops a levee, it is highly likely that the entire section of levee will be damaged and breached, causing significant local flooding," the memo states.

How did it get that way?
Winter storms have long been the bane of those who live in the San Luis Rey River Valley.

In 1916, heavy rain sent a wall of water tearing through the valley, washing out all city bridges and killing four people. According to historical accounts of the flood, the river valley was flooded for two weeks. Downtown was accessible only by boat.

In 1980, another flood cascaded through the area, moving at 7,800 cubic feet per second, according to Army Corps records. That flood caused an estimated $2.23 million in property damage.

In response to the history of flooding, the Army Corps devised a $80 million flood-control project for the river. By 1993, when another severe flood washed through the valley, 5.4 miles of levees had been finished. Though the city lost several homes, officials said flooding could have been much worse.

Today the levee is seven miles long, stretching from the beach east to the Murray Bridge, which carries College Boulevard over the waterway to join with North River Road.

After the levees were installed, the Corps seeded native plants along the riverbed to provide natural habitat for birds and other animals.

Corps spokesman Jay Field said Friday that plans for the flood control project require a management plan to keep plants growing in the river channel under control. However, that management plan is still on the drawing board even though the project has been officially considered finished by the Corps since 2000.

Field said it has taken more than five years of back-and-forth discussions between the Corps and the U.S. Department of Fish and Wildlife to come up with a management plan for the riverbed because, after the plants began to grow, the endangered Bell's vireo bird moved in.

"We unintentionally created a wetlands habitat for the vireo," Field said. "In 1988, before the project began, there were only eight pairs of vireos in the riverbed. Now there are more than 100."

He added that finding a balance between protecting the endangered birds and protecting humans has taken longer than anticipated.

While the federal government tries to decide on the perfect balance, plants in the riverbed continue to grow unchecked.

What's next?
Field said the Corps hopes to finish a long-term management plan for the flood control project by spring of 2006. But, in the meantime, he said, it would like to get started with preliminary clearing efforts this fall. Doing so, Field said, would provide assurance that heavy rain this winter would not cause the worst-case scenario of a levee breach and flooding in Oceanside this winter.

But he said the U.S. Fish and Wildlife Service would have to give its approval.

"We can't act on our own authority, but we're asking them if we might be able to get started," Field said.

Andy Yuen, deputy field supervisor for the U.S. Fish and Wildlife Service's Carlsbad field office, added that his department just received a copy of the Corps' Sept. 27 letter on Friday and had not had time to form an opinion on the request for an emergency action to clear away plants from the riverbed.

"It's a call the Corps would have to make," Yuen said. "Federal agencies are able to move forward on an emergency action without our prior approval."

Field said Friday that it would take at least three weeks to remove the recommended amount of vegetation from the channel. He said doing so can be tedious because workers must be very selective about which plants they can remove.

"It's not like you can just line up a bunch of bulldozers and start ripping everything out of there," Field said. "There are some plants and habitat that can not be touched."

Please contact staff writer Louise Esola at (760) 901-4151 or lesola@nctimes with any further information on this story.

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